Ablation of atrial fibrillation: What can we tell our patients?

EFFECTIVENESS

Crandall et al,³⁵ in an excellent review of the literature, estimated that ablation treatment is successful in approximately 60% to 70% of patients, that 10% to 40% of patients require a second ablation procedure, and that 10% to 15% still need antiarrhythmic drugs.

The specifics of each procedure are beyond the scope of this review, but outcomes have been shown to be better with individualized ablation therapy than with an anatomic approach. Oral et al²⁸ showed that this tailored approach could provide success rates up to 77%; the repeat-procedure rate was 18%, and the risk of complications was low. The tailored approach allows operators to target triggers in locations other than in the pulmonary veins, including those in the thoracic veins and superior vena cava, during mapping. In addition, this approach is often needed in persistent atrial fibrillation, where left atrial substrate is likely to play a larger role than in paroxysmal atrial fibrillation and can be specifically targeted using this method.

When using pulmonary vein isolation by itself, studies have shown better outcomes in treating paroxysmal atrial fibrillation than persistent atrial fibrillation.³⁴ These outcomes have been shown to improve with an individualized approach to ablation therapy.

Haïssaguerre et al³⁶ used various tailored ablation techniques to terminate persistent atrial fibrillation and were able to terminate the rhythm in 87% of their patients. Eleven months after the procedure, 95% of the patients in whom it succeeded remained free of arrhythmia.

Randomized controlled trials now confirm that left atrial ablation is superior to antiarrhythmic drug therapy in maintaining sinus rhythm over time.^19,37,38

COMPLICATIONS

It is important that patients understand the risks associated with the procedure. Advancing technology in imaging and catheters and our growing understanding of atrial fibrillation are not only able to optimize ablation outcomes, but also to minimize complications.

Complications of catheter-based treatment of atrial fibrillation described by the expert consensus committee¹ include:

• Cardiac tamponade
• Pulmonary vein stenosis
• Phrenic nerve injury
• Esophageal injury, atrioesophageal fistula
• Periesophageal vagal injury
• Thromboembolic events
• Vascular complications
• Acute coronary artery occlusion (rare)
• Air emboli from catheters and sheath
• Catheter entrapment in the mitral valve
• Tachyarrhythmias
• Radiation exposure
• Mitral valve trauma.

Cardiac tamponade

Cardiac tamponade due to accidental puncture or excessive heat accumulation, steam expansion, and perforation of the atrial wall occurs in about 6% of patients,²⁰ but this number varies. Limiting the power delivered to tissue to less than 25 or 35 W may reduce the incidence of this complication.¹ The expertise of the physician and the type of imaging used (eg, transesophageal or intracardiac echocardiography) are also factors.

Pulmonary vein stenosis

Pulmonary vein stenosis was seen after the first pulmonary vein isolation techniques were tried, when ablation within the pulmonary vein caused high rates of this complication.¹ Improved knowledge of anatomy and better visualization using intracardiac echocardiography have led to a significantly lower rate of pulmonary vein stenosis.²⁰ The current rate is 0.5% to 2%.^12,20

Nevertheless, it is important for referring physicians to recognize the symptoms of pulmonary vein stenosis, as they will likely be the first providers to see a patient with these symptoms, which can be mistaken for pneumonia or congestive heart failure. The symptoms include cough, dyspnea, pneumonia, and hemoptysis that may occur early or late (weeks) after ablation.

CT, MRI, and ventilation-perfusion scanning can be used to diagnose pulmonary vein stenosis. Its treatment includes stenting the narrowed vein.

Esophageal injury

Esophageal injury, specifically formation of an atrioesophageal fistula, is a life-threatening complication of this treatment.¹ The esophagus passes very close to the left atrial posterior wall and is therefore at risk of thermal injury during ablation.

Health care professionals should be alert to the symptoms of this complication, which include dysphagia, odynophagia, hematemesis, signs of intermittent cardiac or neurologic ischemia, persistent fever, bacteremia, fungemia, leukocytosis, and melena.¹² These symptoms may arise weeks after the procedure.

Any patient who has recently undergone catheter ablation and who presents with some of these symptoms needs a prompt workup with MRI or CT. Endoscopy is contraindicated because it can introduce air into the esophagus, which may result in air embolism to the brain. Atrioesophageal fistula is generally fatal, but emergency surgery may be an option.

Thromboembolism

Thromboembolic events are another worrisome complication. The reported incidence rate ranges between 0% and 7%.¹

Appropriate anticoagulation protocols can minimize the risk. Patients should take warfarin (Coumadin) for at least 3 weeks before undergoing ablation if they have paroxysmal atrial fibrillation and a CHADS₂ score of 1 or higher (1 point each for having congestive heart failure, hypertension, age > 75 years, or diabetes; 2 points for having a prior stroke or transient ischemic attack), or if they have persistent atrial fibrillation regardless of the CHADS₂ score. The target international normalized ratio (INR) is in the therapeutic range, ie, 2 to 3. Patients who have paroxysmal atrial fibrillation and a CHADS₂ score of 0 may be treated with aspirin or warfarin before the procedure. Patients who have been taking warfarin should be “bridged” with subcutaneous low-molecular-weight heparin or intravenous unfractionated heparin before ablation, eg, by stopping the warfarin several days before the procedure and substituting enoxaparin (Lovenox) 0.5 to 1 mg/kg twice daily until the evening before the procedure.

To screen for thrombi in the left atrium, transesophageal echocardiography should be performed before the procedure in patients who have not been receiving warfarin, or whose INRs have not consistently been in the therapeutic range of 2 to 3, or who have persistent atrial fibrillation and are in atrial fibrillation at the time of the procedure.

During the procedure, anticoagulation is maintained with a heparin infusion. After the procedure, warfarin is restarted along with a low-molecular-weight heparin or unfractionated heparin. The heparin is stopped when the INR is in the therapeutic range, but warfarin should be continued for at least 3 months. Selected patients with a CHADS₂ score of 1 may be switched to aspirin therapy after several months, and those with a score of 0 may be switched to aspirin or no therapy.¹²

We still lack data from large-scale trials about long-term thromboembolic complications of ablation therapy. Most electrophysiologists prefer to continue anticoagulation indefinitely and would consider terminating it only with great caution.